Apart from the protective earthing of a casing or modular chassis, with which easily contactable, inactive metal parts are connected to a protective conductor, it is also necessary to have an earthing during the plugging process of a plug-in module, which is contacted with a voltage of 50 V.
It is known to equip connectors with an anticipatory earth contact and by means of the latter to produce a connection between a plug-in module and a protective conductor of the modular chassis. The arrangement and construction of the earth contact are intended to permit an electrical connection before contacting of the other live contacts. During pulling of a module, the electrical connection of the anticipatory earth contact must be interrupted last.
In a known protective conductor connection use is made of a contact spring in the vicinity of a conductive guide of a modular chassis. The contact spring is inserted in the guide, which is generally made from plastic, and produces an electrical connection during the inserting of a plug-in module.
It is disadvantageous in this construction that the contact spring is located within the guide rail and during the insertion does not in each case ensure the necessary anticipatory protective earthing.